cursor: Revise edge cases for the pointer moving towards barriers

Since barriers block the invisible line between pixels, that means
that we need to explicitly check the boundaries, or else we'll have
a potential off-by-one error. This fixes issues when trying to move
down or right across a barrier and having the pointer visibly bounce.

Signed-off-by: Jasper St. Pierre <jstpierre@mecheye.net>
Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>

xfixes/cursor.c

@@ -1093,7 +1093,11 @@ barrier_is_blocking(const struct PointerBarrier * barrier,
         if (dir & BarrierNegativeX && x1 == (barrier->x1 - 1))
             return FALSE;
         /* startpoint adjacent to barrier, moving towards -> block */
-        if (x1 == barrier->x1 && y1 >= barrier->y1 && y1 <= barrier->y2) {
+        if (dir & BarrierPositiveX && x1 == (barrier->x1 - 1) && y1 >= barrier->y1 && y1 <= barrier->y2) {
+            *distance = 0;
+            return TRUE;
+        }
+        if (dir & BarrierNegativeX && x1 == barrier->x1 && y1 >= barrier->y1 && y1 <= barrier->y2) {
             *distance = 0;
             return TRUE;
         }
@@ -1105,7 +1109,11 @@ barrier_is_blocking(const struct PointerBarrier * barrier,
         if (dir & BarrierNegativeY && y1 == (barrier->y1 - 1))
             return FALSE;
         /* startpoint adjacent to barrier, moving towards -> block */
-        if (y1 == barrier->y1 && x1 >= barrier->x1 && x1 <= barrier->x2) {
+        if (dir & BarrierPositiveY && y1 == (barrier->y1 - 1) && x1 >= barrier->x1 && x1 <= barrier->x2) {
+            *distance = 0;
+            return TRUE;
+        }
+        if (dir & BarrierNegativeY && y1 == barrier->y1 && x1 >= barrier->x1 && x1 <= barrier->x2) {
             *distance = 0;
             return TRUE;
         }